FIG. 3 is a view of a wide aluminum wiring layer of a conventional semiconductor integrated circuit device disclosed, for example, in Japanese Patent Application No. 144,176/1979 (Laid open no. 67937/1981). In FIG. 3, the conventional aluminum wiring layer includes aluminum power wiring 1, aluminum ground wiring 2, and slits 3 cut out of the power wiring 1 and the ground wiring 2.
A molded package type semiconductor integrated circuit device having such aluminum wiring develops contraction stress applied from the mold to the circuit device. This stress is absorbed by the slits 3 to reduce the sliding of the aluminum wiring (hereinafter referred to as "aluminum wiring slide"). It is known that increasing the number of the slits decreases the likelihood of aluminum wiring slide occurring. However, while the slits 3 are a good countermeasure to prevent aluminum wiring slide, they are disadvantageous in that they cause current density to increase due to reduction in the effective wiring cross-section (width) as compared with wiring having no slits.
In the conventional semiconductor integrated circuit described above, the wiring widths must be increased as compared to wiring having no slits in order to provide the same current density. That is, the power wiring 1 and the ground wiring 2 must be widened. Since an output buffer transistor for driving an external pin of the device cannot be formed at an arbitrary point under the wirings parts 1 and 2 due to the slits 3, the conventional integrated circuit requires greater area on the substrate. Further, when the distance between the slits 3 is increased to prevent increase in the current density, the possibility of aluminum wiring slide increases.
Heretofore, a bulk contact was used only as a well for forming a transistor. A substrate near the well was used to stabilize the substrate and the well so as to eliminate aluminum wiring slide.
Aluminum wirings were heretofore connected to a lower layer via a through hole or a contact, and an uneven portion was presented under the aluminum wirings. For example, an uneven portion is formed at the crossing and not crossing portions between the bit line and the word line of a DRAM.
The width of aluminum wiring is discussed in "Stress Analysis of Passivation Film Crack for Plastic Molded LSI Caused by Thermal Stress" by S. Okikawa in ISTFA (International Symposium for Testing and Failure Analysis), 1983, pp. 275-280. This paper provides the following conclusions:
(1) The stress of resin in the form of shearing stress on the surface of a chip becomes 9.5 kg/mm.sup.2 at the corner of the chip.
(2) The strength of the passivation film is proportional to bending strength and inversely proportional to the square of the aluminum width.
(3) To prevent a passivation crack, it is preferable to divide the aluminum width into several tens of microns at the corner of a chip subject to large shearing stress. According to the inventor's experiments, passivation cracks as large as 30 microns may occur.